Transparent tantalum oxide glass-ceramics and transparent aluminum tantalate glass-ceramics

ABSTRACT

A transparent glass-ceramic composition including: of the formula Ta2-x AlxO5-x where x is less than 1; of the formula AlTaO4; of the formula AlPO4; a mixture of AlTaO4 and AlPO4; or a mixture of the formula Ta2-x AlxO5-x, AlTaO4, and AlPO4. Also disclosed are transparent glass-ceramic compositions including, for example, a dopant as defined herein, or a supplemental metal oxide or metalloid oxide of MxOy, MxM′x′Oy, or a mixture thereof such as oxides of Nb, Ti, W, B, or Ga, as defined herein. Also disclosed are methods of making the disclosed transparent glass-ceramic compositions, and optical articles, optical components, and optical apparatus thereof.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority of U.S. ProvisionalApplication Ser. No. 62/630,449 filed on Feb. 14, 2018 the contents ofwhich are relied upon and incorporated herein by reference in theirentirety as if fully set forth below.

The entire disclosure of each publication or patent document mentionedherein is incorporated by reference.

BACKGROUND

The disclosure relates to transparent tantalum oxide glass-ceramics andtransparent aluminum tantalate glass-ceramics.

SUMMARY

In embodiments, the disclosure provides a transparent tantalum oxidecontaining glass-ceramic, or a transparent aluminum tantalate containingglass-ceramic.

In embodiments, the disclosure provides a transparent glass-ceramiccontaining tantalum oxide or aluminum tantalate, and additionallyincluding a metal or metal oxide supplement or complement such as Nb,Ti, or W, and more specifically a metal oxide supplement such as Nb₂O₅,TiO₂ or WO₃.

In embodiments, the disclosure provides a transparent glass-ceramiccontaining tantalum oxide or aluminum tantalate, and additionallyincluding a metal or metalloid supplement or complement such as B orB₂O₃ while maintaining or reducing the other glass constituents such asthe Si content.

In embodiments, the disclosure provides a transparent glass-ceramiccontaining tantalum oxide or aluminum tantalate, and additionallyincluding a metal or metalloid supplement or complement such as Ga orGa₂O₃ while maintaining or reducing the other glass constituents such asthe Al content.

In embodiments, the disclosure provides a transparent glass-ceramiccontaining tantalum oxide or aluminum tantalate, and additionallyincluding a performance enhancing dopant.

In embodiments, the disclosure provides a method of making a transparentglass-ceramic from certain Ta-containing aluminophosphosilicate glasses.

In embodiments, the disclosure provides a method of making a transparentglass-ceramic having a major crystalline phase of either Al-containingTa₂O₅ when cerammed at low temperatures, or AlTaO₄ when cerammed at hightemperature.

BRIEF DESCRIPTION OF THE DRAWINGS

In embodiments of the disclosure:

FIGS. 1A and 1B show different X-ray diffraction patterns of the samesource composition 9Ta₂O₅:15 Al₂O₃:6P₂O₅:70SiO₂ that was separatelycerammed under different conditions of: 925° C. for 2 hrs (FIG. 1A); and1075° C. for 2 hrs (FIG. 1B).

FIG. 2 shows a ²⁷Al MAS NMR spectrum of glass 1 (Example 4 in Table 1),cerammed at 950° C. for 2 hrs.

FIGS. 3A and 3B show TEM photomicrograph images of glass 1 (Example 4 inTable 1).

FIG. 4 shows dependence of Young's modulus (E) versus the ceramtemperature for a composition of the formula:9Ta₂O₅:15Al₂O₃:6P₂O₅:70SiO₂ of Example 4 in Table 1.

FIG. 5 shows hardness (H) versus the ceram temperature for a compositionof the formula: 9Ta₂O₅:15Al₂O₃:6P₂O₅:70SiO₂ of Example 4 in Table 1.

FIG. 6 shows the refractive index (nD or nD) versus the ceramtemperature for a composition of the formula:9Ta₂O₅:15Al₂O₃:6P₂O₅:70SiO₂ of Example 4. in Table 1

FIGS. 7A and 7B show the ³¹P MAS NMR spectra and the ²⁷Al MAS NMRspectra, respectively, for the precursor glass of Example 1 in Table 1.

FIGS. 8A and 8B show the ³¹P MAS NMR and ²⁷Al MAS NMR, respectively, forthe cerammed glass of Example 1 in Table 1.

FIGS. 9A and 9B show the ³¹P MAS NMR and the ²⁷Al MAS NMR spectra,respectively, of Example 4 in Table 1 after a ceramming treatmentdefined as Schedule 1 (“925/2”).

FIGS. 10A and 10B show the ³¹P MAS NMR and the ²⁷Al MAS NMR spectra,respectively, of Example 4 in Table 1 after a ceramming treatmentdefined as Schedule 3 (“1075/2” only).

FIGS. 11A and 11B show the effect of increasing the cerammingtemperature on phase assemblage in the disclosed method of making.

DETAILED DESCRIPTION

Various embodiments of the disclosure will be described in detail withreference to drawings, if any. Reference to various embodiments does notlimit the scope of the invention, which is limited only by the scope ofthe claims attached hereto. Additionally, any examples set forth in thisspecification are not limiting and merely set forth some of the manypossible embodiments of the claimed invention.

In embodiments, the disclosed compositions, and methods of making andusing provide one or more advantageous features or aspects, includingfor example as discussed below. Features or aspects recited in any ofthe claims are generally applicable to all facets of the invention. Anyrecited single or multiple feature or aspect in any one claim can becombined or permuted with any other recited feature or aspect in anyother claim or claims.

Definitions

“Ta₂O₅” has two different but related meanings in the presentdisclosure. In batch or source ingredient circumstances “Ta₂O₅” refersto a source of Ta₂O₅. In cerammed transparent glass-ceramic compositioncircumstances “Ta₂O₅” refers to Ta_(2-x)Al_(x)O_(5-x) where x issignificantly less than 1, as defined herein.

“Include,” “includes,” or like terms means encompassing but not limitedto, that is, inclusive and not exclusive.

“About” modifying, for example, the quantity of an ingredient in acomposition, concentrations, volumes, process temperature, process time,yields, flow rates, pressures, viscosities, and like values, and rangesthereof, or a dimension of a component, and like values, and rangesthereof, employed in describing the embodiments of the disclosure,refers to variation in the numerical quantity that can occur, forexample: through typical measuring and handling procedures used forpreparing materials, compositions, composites, concentrates, componentparts, articles of manufacture, or use formulations; through inadvertenterror in these procedures; through differences in the manufacture,source, or purity of starting materials or ingredients used to carry outthe methods; and like considerations. The term “about” also encompassesamounts that differ due to aging of a composition or formulation with aparticular initial concentration or mixture, and amounts that differ dueto mixing or processing a composition or formulation with a particularinitial concentration or mixture.

“Optional” or “optionally” means that the subsequently described eventor circumstance can or cannot occur, and that the description caninclude instances where the event or circumstance occurs and instanceswhere it does not.

The indefinite article “a” or “an” and its corresponding definitearticle “the” as used herein means at least one, or one or more, unlessspecified otherwise.

Abbreviations, which are well known to one of ordinary skill in the art,may be used (e.g., “h” or “hrs” for hour or hours, “g” or “gm” forgram(s), “mL” for milliliters, and “rt” for room temperature, “nm” fornanometers, and like abbreviations).

Specific and preferred values disclosed for components, ingredients,additives, dimensions, conditions, times, and like aspects, and rangesthereof, are for illustration only; they do not exclude other definedvalues or other values within defined ranges. The composition andmethods of the disclosure can include any value or any combination ofthe values, specific values, more specific values, and preferred valuesdescribed herein, including explicit or implicit intermediate values andranges.

Glass-ceramics are well known as materials that provide the excellentproperties of polycrystalline ceramics and the possibility of zeroporosity and the ability to make complex shapes via traditional glassforming techniques. However, most glass-ceramics are opaque due to thedifficulty of: maintaining the size of the crystallite population belowvisible light wavelengths; minimizing the refractive index contrastbetween the dominant crystal phase and residual glass; or both. Sometransparent glass-ceramic “families” are known, notably the β-quartz andpetalite glass-ceramics from the Li aluminosilicate system and themullite glass-ceramics from the aluminosilicate system, but they arerelatively rare. Even rarer are transparent glass-ceramics where themajor crystalline phase is a non-silicate, with the only major examplebeing the spinel glass-ceramics from the Zn/Mg aluminosilicate system.Such materials are of particular interest for scratch-resistant coverglass applications, fluorescence applications when doped withoptically-active transition metal or rare earth ions, and likeapplications. Other unknown transparent glass-ceramic systems having anon-silicate major phase are of interest.

U.S. Pat. No. 7,323,426, entitled HIGH STRAIN POINT GLASSES, mentions afamily of glasses from the SiO₂—Al₂O₃—P₂O₅ ternary system exhibitinghigh strain point, transparency, and low coefficients of thermalexpansion. The glasses have the following composition, expressed in molpercent and calculated from the glass batch on an oxide basis: 55 to 80%SiO₂, 12 to 30% Al₂O₃, and 2 to 15% P₂O₅.

In embodiments, the disclosure provides a transparent glass-ceramiccomposition (i.e., the Si—Al—Ta—P transparent glass-ceramiccompositions) comprising:

-   -   65 to 75% SiO₂;    -   10 to 25% Al₂O₃;    -   5 to 15% Ta₂O₅; and    -   3 to 10% P₂O₅, based on 100 mol % total.

In embodiments, the disclosure provides a transparent glass-ceramiccomposition comprising, for example, 70% SiO₂, 14.5% Al₂O₃, 7.5% P₂O₅,and 8% Ta₂O₅ based on 100 mol % total.

In embodiments, the glass-ceramic composition can further comprise, forexample, SnO₂ in from 0.01 to 2 mol %, by inclusion in the total 100 mol% (i.e., not super addition).

In embodiments, the Ta₂O₅ content in the transparent glass-ceramiccomposition can be, for example, of from 5 to 14 mol %, or of from 8 to12 mol %, including intermediate values and ranges.

In embodiments, the transparency (i.e. allowing passage of light, e.g.,some or most wavelengths in visible spectrum, about 390 to 700 nm) ofthe composition can be demonstrated when, for example, the compositionis cast as a one half inch thick specimen and is generally visibly clearto, for example, a human viewer or other trained observer.

In embodiments, the disclosed transparent composition has a refractiveindex that can be, for example, of from 1.55 to 1.61; the elasticmodulus can be, for example, of from 50 to 95 GPa; and the hardness canbe, for example, of from 6 to 9 GPa.

In embodiments, the disclosed transparent composition can have acrystallite size, for example, of from 5 to 25 nm, includingintermediate values and ranges.

In embodiments, the disclosure provides transparent glass-ceramiccompositions having a portion such as from 0.1 to 50 mol % of the Tacontent of the above mentioned Si—Al—Ta—P transparent glass-ceramiccompositions supplemented (i.e., partially substituted or replaced) orcomplemented (i.e., an ingredient that completes the composition) with,for example, Nb, Ti, or W, to produce Si—Al—Ta—P—Nb transparentglass-ceramic compositions, Si—Al—Ta—P—Ti transparent glass-ceramiccompositions, or Si—Al—Ta—P—W transparent glass-ceramic compositions.

In embodiments, the disclosure provides a metal supplemented transparentglass-ceramic composition comprising, for example:

-   -   65 to 75% SiO₂;    -   10 to 25% Al₂O₃;    -   4 to 7.5% Ta₂O₅;    -   0.01 to 7.5% M_(x)O_(y) or M_(x)M′_(x)O_(y); and    -   3 to 10% P₂O₅, based on 100 mol % total,        wherein in the formulas M_(x)O_(y) or M_(x)M′_(x′)O_(y), M or M′        is selected from the group of a source of Nb, Ti, W, Al, B, Ga,        or a mixture thereof, x and x′ are independently an integer from        1 to 2, and y is an integer from 1 to 5. M_(x)O_(y) can be, for        example, Nb₂O₅, TiO₂, WO₃, and like oxides. M_(x)M′_(x)O_(y) can        be, for example, Al₂TiO₅, B₂O₃, Ga₂O₃, and like oxides, which        metal oxide or metalloid oxide can provide a primary or        supplemental source of TiO₂, Al₂O₃, or like oxides. In        embodiments, the M_(x)O_(y) can have, for example, a formal        valence of 4⁺, 5⁺, or 6⁺.

In embodiments, a transparent glass-ceramic composition can have a metal(M) supplement of a Nb source and the Nb can be present in an amount offrom 0.1 to 50 mol % of the Ta content, and 4 to 7.5% Ta₂O₅ and 0.01 to7.5% Nb in the composition. The supplementation with Nb produces aSi—Al—Ta—P—Nb transparent glass-ceramic composition.

In embodiments, a transparent glass-ceramic composition can have a metal(M) supplement of a Ti source and the Ti can be present in an amount offrom 0.1 to 25 mol % of the Ta content, and 4 to 11.25 mol % Ta₂O₅ and0.01 to 3.75 mol % Ti in the composition. The supplementation with Tiproduces a Si—Al—Ta—P—Ti transparent glass-ceramic composition.

In embodiments, a transparent glass-ceramic composition can have a metal(M) supplement of a W source and the W can be present in an amount offrom 0.1 to 25 mol % of the Ta content, and 4 to 11.25 mol % Ta₂O₅ and0.01 to 3.75 mol % Win the composition. The supplementation with Tiproduces a Si—Al—Ta—P—W transparent glass-ceramic composition.

In embodiments, the disclosed transparent glass-ceramic composition canfurther comprise, for example, a dopant in an amount of 1 mol % or less,for example, of from 0.01 to 1 mol %, of from 0.1 to 0.9 mol %, of from0.1 to 0.85 mol %, of from 0.5 to 0.8 mol %, of from 0.5 to 0.75 mol %,including intermediate values and ranges, based on the 100 mol %. Thedopant can be selected from the group of, for example, a Cr oxide, a Nioxide, a Co oxide, a rare earth oxide, or mixtures thereof. Otherdopants of interest can include, for example, Ti, V, Mn, Cu, Er, andlike oxide dopants, or mixtures thereof.

In embodiments, the oxide dopant can be, for example, selected fromCr₂O₃, NiO, CoO, Er₂O₃, or a mixture thereof.

In embodiments, the resulting transparent glass-ceramic compositionpreferably contains at least 5 mol % or more of Ta₂O₅, which permits theglass-ceramic composition to be a transparent glass-ceramic product.

In preferred embodiments, the resulting transparent glass-ceramiccomposition preferably contains at least about 10 mol % Ta₂O₅.

In other more preferred embodiments, the resulting transparentglass-ceramic composition preferably contains at least about 8 mol %Ta₂O₅.

In embodiments, the precursor glass preferably contains at least 3 mol %or more of P₂O₅, which P₂O₅ content permits the precursor glass to meltat or below 1650° C., and avoids phase separation and opacity in theresulting transparent glass-ceramic composition.

In embodiments, the disclosure provides a more preferred transparentglass-ceramic composition comprising:

-   -   65 to 72% SiO₂;    -   10 to 20% Al₂O₃;    -   4 to 9% P₂O₅; and    -   8 to 13% Ta₂O₅, based on 100 mol %.

In embodiments, an example of the more preferred transparentglass-ceramic composition can be, for example:

-   -   70% SiO₂;    -   14.5% Al₂O₃;    -   7.5% P₂O₅; and    -   8 to 13% Ta₂O₅, based on 100 mol % total.

In embodiments, the composition of the crystalline phase of the morepreferred transparent glass-ceramic composition can be, for example: ofthe formula Ta_(2-x)Al_(x)O_(5-x) where x is less than 1 such as x is offrom 0.001 to 0.2, 0.01 to 0.15, 0.01 to 0.1, including intermediatevalues and ranges.

In embodiments, x in the formula Ta_(2-x)Al_(x)O_(5-x) can be, forexample, from about 0.001 to about 0.99 mol %, from about 0.01 to about0.9 mol %, from about 0.1 to about 0.8 mol %, from about 0.1 to about0.7 mol %, from about 0.1 to about 0.6 mol %, and from about 0.1 toabout 0.5 mol %, including intermediate values and ranges.

In embodiments, the disclosed transparent glass-ceramic composition hasa crystallite size of from 5 to 25 nm.

In embodiments, the disclosure provides a boron supplemented orcomplemented transparent glass-ceramic composition comprising:

-   -   60 to 70% SiO₂;    -   10 to 25% Al₂O₃;    -   4 to 7.5% Ta₂O₅;    -   0.01 to 5% B₂O₃; and    -   3 to 10% P₂O₅, based on 100 mol % total,

In embodiments, the SiO₂ content can be partially supplemented orreplaced by, for example, of from 0.01 to 5 mol % B₂O₃.

In embodiments, the disclosure provides a gallium supplemented orcomplemented transparent glass-ceramic composition comprising:

-   -   65 to 75% SiO₂;    -   2 to 17% Al₂O₃;    -   4 to 7.5% Ta₂₀s;    -   0.01 to 8% Ga₂O₃; and    -   3 to 10% P₂O₅, based on 100 mol % total,

In embodiments, Al₂O₃ can be partially supplemented or replaced by, forexample, of from 0.1 to 8 mol % Ga₂O₃. In supplemental amounts ofgreater than of from 8 mol % Ga₂O₃ there may be some objectionableopalization of the precursor glasses and opacity in the resultantglass-ceramics.

In particularly preferred embodiments, the disclosure provides a methodof making the aforementioned transparent glass-ceramic composition,comprising, for example:

-   -   ceramming a suitable precursor glass composition at 900 to        950° C. for about 2 hrs, to produce a transparent glass-ceramic        of the formula Ta_(2-x)Al_(x)O_(5-x) where x in this formula is        less than 1.

In embodiments, the method of making the aforementioned transparentglass-ceramic composition, can further comprise, for example, includinga dopant in an amount of 1 mol % or less based on the 100 mol % of thesuitable precursor glass composition, and the dopant can be selected,for example, from the group of a Cr oxide, a Ni oxide, a Co oxide, arare earth oxide, or a mixture thereof. Other dopants can include, forexample, Ti, V, Mn, Cu, Er, and like dopants, such as their oxides andlike sources, or mixtures thereof.

In preferred embodiments, a method of making the aforementionedtransparent glass-ceramic composition, can comprise, for example:

-   -   ceramming a suitable precursor glass composition at, for        example, of from 1000 to 1100° C. for about 2 hrs, to produce a        transparent glass-ceramic of the formula of a mixture of AlTaO₄        and AlPO₄ (i.e., AT+AP). A suitable precursor glass composition        can be, for example, the aforementioned preferred or more        preferred transparent glass-ceramic composition.

In embodiments, the method of making any of the preceding transparentglass-ceramic compositions, can further comprise, for example: includinga dopant in an amount of 1 mol % or less based on the 100 mol % total ofthe suitable precursor glass composition, and the dopant can beselected, for example, from the group of a Cr oxide, a Ni oxide, a Cooxide, a rare earth oxide, or mixtures thereof. Other transition metaldopants can include, for example, Cr, Ni, Co, V, Mn, Cu, Er, and likeoxide dopants or equivalent metal sources, or mixtures thereof.

When cerammed at low temperatures, the disclosed transparentglass-ceramics are believed to be the first known glass-ceramics,transparent or opaque, which include Al-containing Ta₂O₅ as the dominantcrystal phase. The transparency of these materials is particularlyremarkable and unexpected in view of the large refractive index contrastor difference between the Ta-containing crystalline phases and thesilica-rich residual glass.

In embodiments, the present disclosure is advantaged in several aspects,including for example: the presence of Ta in the crystalline phasescauses these materials to have a higher refractive index than othertransparent glass-ceramics (e.g., spinel: 1.586). Other transparentglass-ceramics can become translucent or opaque when heated above 1000°C. Unexpectedly, the presently disclosed glass-ceramic compositionsretain their transparency to at least 1100° C. In addition, thepresently disclosed glass-ceramic compositions provide a uniquecrystalline environment for transition metal dopants and allow one totailor the luminescent properties of the transparent glass-ceramics. Thecrystalline environment can provide a host site, for example, for atransition metal dopant or rare earth dopant.

In embodiments, the present disclosure provides a transparent Ta₂O₅glass-ceramic, a transparent AlTaO₄ glass-ceramic, a transparentglass-ceramic containing a mixture of Ta₂O₅ and AlTaO₄, or a mixturethereof. These disclosed glass-ceramics can be made by, for example,heat treatment of a suitable precursor glass having a compositioncomprising or consisting of, for example: 5 to 15% Ta₂O₅, 10 to 25%Al₂O₃, 3 to 10% P₂O₅, and 65 to 75% SiO₂ based on a 100 mol % total. Theprecursor glasses, but not glass-ceramics, having these compositionswere disclosed in the above-mentioned U.S. Pat. No. 7,323,426.

In the present disclosure when exemplary precursor glasses wereindividually cerammed at temperatures of from 900 to 950° C., thecrystalline phase has the Ta₂O₅ structure (FIG. 1A). However, the ²⁷AlMAS NMR spectra of such materials show that this crystalline phasecontains some aluminum (Al) in solid solution (FIG. 2) and itscomposition is better described by the formula Ta_(2-x)Al_(x)O_(5-x),where x in this formula is less than 1. Maximum transparency of theseTa_(2-x)Al_(x)O_(5-x) glass-ceramics is observed when their glassprecursors are cerammed at temperatures in the lower portion of theabove-mentioned range, i.e., 900 to 950° C. When heat treated attemperatures above 900 to 950° C. but below 1,000° C., the resultingTa_(2-x)Al_(x)O_(5-x) glass-ceramics can become slightly hazy. Asindicated in the accompanying Table 1 and Table 2, theseTa_(2-x)Al_(x)O_(5-x) glass-ceramics are characterized by an elasticmodulus of from 77 to 91 GPa.

When the precursor glasses are cerammed at top temperatures in the rangeof from about 975 to 1000° C., the crystalline assemblage of theresultant transparent glass-ceramics are a mixture ofTa_(2-x)Al_(x)O_(5-x) and AlTaO₄. While not bound by theory, it isbelieved that Ta_(2-x)Al_(x)O_(5-x) gradually reacts with residual glassto form AlTaO₄ in response to heating in this temperature range. Withincreasing top temperature, the volume fraction of AlTaO₄ increasesrelative to that of Ta_(2-x)Al_(x)O_(5-x) based on XRD results.

When the precursor glasses are cerammed at top temperatures in of fromabout 1025 to 1050° C., the crystalline assemblage of the resultanttransparent glass-ceramics are a mixture of Ta_(2-x)Al_(x)O_(5-x),AlTaO₄, and AlPO₄. With increasing top temperature, the volume fractionof AlTaO₄ continues to increase relative to that ofTa_(2-x)Al_(x)O_(5-x) as the reaction between the Ta_(2-x)Al_(x)O_(5-x)phase and residual glass progresses towards completion.

When the precursor glasses are cerammed at top temperatures of fromabout 1075 to 1100° C., the crystalline assemblage can be, for example,a mixture of AlTaO₄ and AlPO₄ (FIG. 1B). The transparency of theseAlTaO₄ glass-ceramics is comparable to the transparency of theTa_(2-x)Al_(x)O_(5-x) glass-ceramics cerammed at 900 to 925° C., in partdue to the AlTaO₄ crystallites being on the order of 15 nm in diameter(FIG. 3). However, the elastic modulus of the AlTaO₄+AlPO₄glass-ceramics (e.g., 54 to 79 GPa) is typically lower than that of theTa_(2-x)Al_(x)O_(5-x) glass-ceramics (e.g., 77 to 91 GPa).

Referring to the Figures, FIGS. 1A and 1B show different X-raydiffraction patterns of the same source composition 9Ta₂O₅:15Al₂O₃:6P₂O₅:70SiO₂ that was separately cerammed under differentconditions of: 925° C. for 2 hrs (FIG. 1A); and 1075° C. for 2 hrs (FIG.1B). FIG. 1A shows an X-ray diffraction pattern of glass 1, which isExample 4 in Table 1, cerammed at 925° C. for 2 hrs; the crystal phaseis Ta_(2-x)Al_(x)O_(5-x). FIG. 1B shows an X-ray diffraction pattern ofglass 1, which is Example 4 in Table 1, cerammed at 1075° C. for 2 hrs;the crystal phases are AlTaO₄ and AlPO₄.

FIG. 2 shows a ²⁷Al MAS NMR spectrum of glass 1, which is Example 4 inTable 1, cerammed at 950° C. for 2 hrs, has a sharp peak near 0 ppm thatshows the presence of six-coordinated aluminum in a crystallineenvironment, and a broad main peak near 40 ppm that shows the presenceof four-coordinated aluminum in a glassy environment. Fitting the datain FIG. 2 indicated that 15% of the Al₂O₃ is 6-coordinated (for a ²⁷AlMAS NMR alumina film study see: A. Gleizes, et al., “TemperatureDependent 4-, 5- and 6-Fold Coordination of Aluminum in MOCVD-GrownAmorphous Alumina Films: From Local Coordination to Material Properties.Advances in Science and Technology, 2014, vol. 91, pp. 123-133).

FIGS. 3A and 3B show TEM photomicrograph images of glass 1, which isExample 4 in Table 1. The image in FIG. 3A was obtained from thecomposition (Example 4, Table 1, FIG. 1A) that was cerammed at schedule1 (925° C. for 2 hrs) where the crystal phase is Ta_(2-x)Al_(x)O_(5-x)and the crystallite sizes are about 5 to 15 nm. The image in FIG. 3B wasobtained from a composition (Example 4, Table 1) that was cerammed atschedule 2 (875° C. for 2 hrs followed by 1075° C. for 2 hrs) where thecrystalline assemblage is AlTaO₄ and AlPO₄, and the crystallite size isof from 15 to 25 nm.

FIGS. 7A and 7B show the ³¹P MAS NMR and the ²⁷Al MAS NMR, respectively,for the precursor glass of Example 1 in Table 1. Both the ³¹P and ²⁷Almagic-angle spinning nuclear magnetic resonance (MAS NMR) spectra of theprecursor glass Example 1 in Table 1, have broad NMR signals, andconfirm the absence of any crystalline Al- or P-containing phases in theannealed glass.

FIGS. 8A and 8B show the ³¹P MAS NMR and the ²⁷Al MAS NMR, respectively,for the cerammed glass of Example 1 in Table 1.

The ceramming of Example 1 in Table 1 was accomplished at 925/2 then1125/4, which ceramming schedule is similar but not identical toSchedule 2. The ³¹P MAS NMR contains an intense, relatively sharp peakat −29 ppm. The position and shape of this peak is generally consistentwith crystalline AlPO₄, in agreement with the XRD and ²⁷Al NMR data onsimilar samples. The P speciation, as measured by ³¹P MAS NMR, isapproximately 90% in crystalline AlPO₄ and 10% in residual glass, theresidual glass is evident from the two weak signals around −35 to −37ppm. The ²⁷Al MAS NMR data has two sharp peaks at 40 and 5 ppm, and the40 ppm signal is consistent with four-coordinated Al in crystallineAlPO₄, and the 5 ppm signal is consistent with six-coordinated Al incrystalline AlTaO₄. These ²⁷Al NMR data indicate about 50% of Al₂O₃ inAlPO₄, about 40% of Al₂O₃ in AlTaO₄ and up to about 10% of Al₂O₃ inresidual glass. The Al₂O₃ in residual glass is a weak, broad signal thatlies under the AlPO₄ resonance at 40 ppm. Based on the peak areas in the²⁷Al NMR data, 90 to 95% of the P₂O₅ is crystallized as AlPO₄, and 70 to75% of the Ta₂O₅ is crystallized as AlTaO₄. The residual glass is silicarich, with a small amount of Al₂O₃ and Ta₂O₅, and a negligible amount ofP₂O₅.

FIGS. 9A and 9B show the ³¹P MAS NMR and the ²⁷Al MAS NMR spectra,respectively, of Example 4 in Table 1 after a ceramming treatmentdefined as Schedule 1 (“925/2”).

The ³¹P MAS NMR data (9A) contain an intense, single resonance fromamorphous phosphate groups. The ²⁷Al MAS NMR spectrum (9B) is comprisedof two peaks: the left peak is relatively broad and intense, consistentwith four-coordinated Al in the glass, and the right peak at 3 ppm issignificantly narrower and assigned to six-coordinated Al in crystallineTa_(2-x)Al_(x)O_(5-x). This sample after Schedule 1 ceramming has about88% of Al₂O₃ in residual glass and 12% of Al₂O₃ in theTa_(2-x)Al_(x)O_(5-x) crystalline phase.

FIG. 2 and FIG. 9B are very similar but are not exactly the same. FIG. 2and FIG. 9B both represent ²⁷Al NMR of Example 4 in Table 1, but withceramming at two different temperatures: 950/2 (FIG. 2) and 925/2 (FIG.9). The results are nearly the same and confirm that Al partially entersthe crystalline Ta_(2-x)Al_(x)O_(5-x) phase and exhibits sometemperature dependence on the amount of Al in this phase. Additionally,the ³¹P NMR data in FIG. 9A indicate that P speciation is unaffected by“Schedule 1” and similar nucleation treatments.

FIGS. 10A and 10B show the ³¹P MAS NMR and ²⁷Al MAS NMR spectra,respectively, of Example 4 in Table 1 after a ceramming treatmentdefined as Schedule 3 (“1075/2” only). The ³¹P NMR data (FIG. 10A)contain an intense, relatively sharp peak at −29 ppm. The position andshape of this peak are generally consistent with crystalline AlPO₄, inagreement with the XRD and ²⁷Al NMR data on similar samples. The Pspeciation, as measured by ³¹P MAS NMR, is approximately 85% incrystalline AlPO₄ and 15% in residual glass. The 15% in residual glassis evident from the two weak signals around −35 to −40 ppm. The ²⁷Al MASNMR data (FIG. 10B) are comprised of two sharp peaks at 40 and 5 ppm.The 40 ppm peak is consistent with four-coordinated Al in crystallineAlPO₄, and the 5 ppm peak is consistent with six-coordinated Al incrystalline AlTaO₄. These ²⁷Al NMR data indicate 35% of Al₂O₃ in AlPO₄,45% of Al₂O₃ in AlTaO₄, and up to 20% of Al₂O₃ in residual glass. The upto 20% of Al₂O₃ in residual glass is reflected in a weak, broad signalthat lies under the AlPO₄ resonance at 40 ppm. Based on the peak areasin the ²⁷Al NMR data, 85 to 90% of the P₂O₅ is crystallized as AlPO₄,and 75% of the Ta₂O₅ is crystallized as AlTaO₄. The residual glass issilica rich, with a small amount of Al₂O₃ and Ta₂O₅, and a negligibleamount of P₂O₅.

Examples

The following Examples demonstrate making, use, and analysis of thedisclosed glass-ceramics and methods in accordance with the abovegeneral procedures. The following are representative of preparative andcomparative preparative examples followed by a characterization example.The Tables 1, 2, and 3 list representative composition examplesidentified in the table headers. The Table 4 lists crystallineassemblage(s) present at selected ceram temperatures. The Table 5 listsboron-containing Ta₂O₅ or AlTaO₄ transparent glass-ceramics; andGa-containing Ta₂O₅ or AlTaO₄ transparent glass-ceramics.

Preparative Example 1

Preparation of Precursor Glass The precursor glasses were made bymelting 800 g ball milled batches of the respective oxides and aluminummetaphosphate, with or without a dopant, in 650 cc Pt crucibles at 1650°C. for 16 to 20 hrs. The molten batches were quenched to glass bypouring onto steel. The glasses were then annealed at 800° C.

Preparative Example 2

Preparation of Glass-ceramics Glass-ceramics were prepared by cuttingthe annealed precursor glass of Example 1 into pieces and subjecting thepieces to a one-step or a two-step ceram schedule in the range of 875 to1100° C. For the purposes of property evaluation, one of three cerammingschedules (1, 2, or 3) defined herein was used.

A number of ceramming schedules were investigated, including a two hrhold at every 25° from 900 and 1100° C. (see also Preparative Example 3and Table 4). All 2 hr hold ceram schedules yielded transparentglass-ceramics. In embodiments, it can be sufficient to ceram by heatingat a high temperature, e.g., 1,000 to 1,100° C. or more for less than 1hr.

Ceram Schedule 1 was: heating the suitable precursor glass pieces at 8°C./min to 925° C., hold at 925° C. for 2 hrs, followed by cooling atfurnace rate to ambient temperature of about 25° C. (abbreviated in theTables as “925/2”=Schedule 1).

Ceram Schedule 2 was: heating at 8° C./min to 875° C., hold at 875° C.for 2 hrs (i.e., a nucleation step), heating at 8° C./min to 1075° C.,hold at 1075° C. for 2 hrs (i.e., a crystal growth step) (abbreviated inthe Tables as the hold temperature (° C.) and the hold time (hr) ratiossuch as “875/2” and then “1075/2” defines Schedule 2; or alternatively“1075/2” only is Schedule 3), followed by cooling at furnace rate toambient temperature of about 25° C. The heating at 8° C./min to 875° C.,hold at 875° C. for 2 hrs (i.e., a nucleation step) can be optional,that is unnecessary, since the glass may already have beenpre-nucleated, i.e., chemically segregated as indicated by transmissionelectron microscopy, and either Schedule 2 or Schedule 3 is believed toproduce the same product as measured by XRD. However, comparativeproperty measurements for glass-ceramics with and without the 875° C.hold are presently unavailable and could indicate significantdifferences in the compositions.

Preparative Example 3

Influence of Ceram Condition on Crystalline Phase Assemblage of theGlass-Ceramics Preparative Example 3 is a study that demonstrates theeffect on the crystalline phase assemblage of tabulated Example 4 ofTable 1 by raising the 2 hr ceram temperature from 900 to 1100° C. inincrements of 25°. Example 4 of Table 1 had an initial composition of9Ta₂O₅:15Al₂O₃:6P₂O₅:70SiO₂. FIGS. 11A and 11B show the effect ofincreasing the ceram temperature on phase assemblage in the disclosedmethod of making. The influence of ceram temperature on phase assemblageis shown in XRD patterns of the FIGS. 11A and 11B. FIG. 11A is acomposite plot (i.e., an overlay for comparison) of the XRD patterns forascending ceram temperatures 900, 925, 950, 975, or 1,000° C. FIG. 11Bis also a composite plot (i.e., an overlay for comparison) of the XRDpatterns for ascending ceram temperatures 1,000, 1,025, 1,050, 1,075, or1,100° C. The XRD data shows that ceramming at 900, 925, or 950° C. for2 hr yields “Ta₂O₅” (i.e., Ta_(2-x)Al_(x)O_(5-x)) as the solecrystalline phase. However, the increasing intensity of the major peakat 23° on raising the temperature from 900 to 925 to 950° C. indicatesthat the glass-ceramic contains a higher weight fraction or highervolume fraction of “Ta₂O₅” (i.e., Ta_(2-x)Al_(x)O_(5-x)) and a lowerweight fraction or lower volume fraction of residual glass when cerammedat the higher temperatures in the range of 900 to 950° C. Afterceramming at 975° C., the resulting glass-ceramic consists mainly of“Ta₂O₅” (i.e., Ta_(2-x)Al_(x)O_(5-x)) plus residual glass. However,there is a pronounced shoulder at about 24.5° indicating that AlTaO₄ hasbegun to crystallize and indicates the onset of the reaction of “Ta₂O₅”(i.e., Ta_(2-x)Al_(x)O_(5-x)) and residual glass to produce AlTaO₄. By1000° C./2, the 24.5° shoulder is now a resolved peak. With a furtherincrease in ceram temperature above 1000° C., the relative intensity ofthe main “Ta₂O₅” (i.e., Ta_(2-x)Al_(x)O_(5-x)) peak at 23° decreases,and the peak at 24.5° representing the main AlTaO₄ peak increasesfurther. These XRD changes indicate the gradual conversion of “Ta₂O₅”(i.e., Ta_(2-x)Al_(x)O_(5-x)) and glass into AlTaO₄ with increasingtemperature. This crystalline phase conversion appears to be complete by1050° C. In addition, the appearance of an XRD diffraction peak at 21°in the 1025° C./2 sample signals the first appearance of AlPO₄ as anadditional crystalline phase. AlPO₄ is present at all higher ceramtemperatures. Table 4 summarizes the crystalline assemblage present atthe selected ceram temperatures. The left to right listing of phases inTable 4 indicates their approximate relative abundance, e.g., for the1025/2 sample, AlTaO₄ is the most abundant phase, followed by “Ta₂O₅”(i.e., Ta_(2-x)Al_(x)O_(5-x)), and AlPO₄ is the least abundant (i.e.,AlTaO₄>Ta₂O₅>AlPO₄).

Comparative Preparative Example 3

A comparative glass having the formula: 4Ta₂O₅:18.5Al₂O₃:7.5P₂O₅:70SiO₂,was prepared. The glass had a Ta₂O₅ content of below 5 mol %. This glassremains fully glassy, i.e., no crystalline phase was observed visuallyor by XRD when cerammed at temperatures as high as 1100° C.

Preparative Example 4

Gallium (Ga) was selected as a supplemental metal or metalloid forinclusion in a composition containing Al (and the Al₂O₃ content in thebatch was reduced accordingly) in either of the phases, if present, of“Ta₂O₅” (i.e., Ta_(2-x)Al_(x)O_(5-x)) or AlPO₄. Table 5 lists threesupplemental examples of Ga-containing Ta₂O₅ or AlTaO₄ transparentglass-ceramics.

Preparative Example 5

Similarly, boron (B) such as B₂O₃ was selected as a supplemental metalor metalloid for inclusion in a composition containing SiO₂ (and theSiO₂ content was reduced accordingly) in a transparent glass-ceramiccomposition which includes Ta₂O₅, Al₂O₃, P₂O₅ and SiO₂. Table 5 liststwo supplemental examples of boron-containing Ta₂O₅ or AlTaO₄transparent glass-ceramics.

Supplementing with Ga or B as indicated in Preparative Examples 4 and 5,respectively, had the advantage of lowering the viscosity at the meltingand forming temperatures. However, the Ga or B supplemented compositionswere disadvantaged by producing noticeable haze, particularly inglass-ceramics made at 925° C. (e.g., slight haze).

Characterization Example

Characterization of Young's elastic modulus (E), hardness (H), orrefractive index (nD or nD) for a transparent glass-ceramic compositionof the molecular formula 9Ta₂O₅:15Al₂O₃:6P₂O₅:70SiO₂.

FIG. 4 shows dependence of Young's modulus (E) versus the ceramtemperature for a composition of the formula:9Ta₂O₅:15Al₂O₃:6P₂O₅:70SiO₂ of Example 4 in Table 1.

FIG. 5 shows hardness (H) versus the ceram temperature for a compositionof the formula: 9Ta₂O₅:15Al₂O₃:6P₂O₅:70SiO₂ of Example 4 in Table 1.

FIG. 6 shows the refractive index (nD or nD) versus the ceramtemperature for a composition of the formula:9Ta₂O₅:15Al₂O₃:6P₂O₅:70SiO₂ of Example 4 in Table 1.

In each of FIGS. 4 to 6, the points at 800° C. correspond to theannealed, uncerammed glass. The points at 925° C. correspond to aTa_(2-x)Al_(x)O_(5-x) glass-ceramic made using the 925/2 schedule. Thepoints at 1075° C. corresponds to a combined or a mixed AlTaO₄ and AlPO₄glass-ceramic made using the combined 875/2 and 1075/2 ceram schedule 2above. The E, H, and nD values are higher for the Ta_(2-x)Al_(x)O_(5-x)(925° C.) glass-ceramic than for the mixed AlTaO₄ and AlPO₄ (1075° C.)glass-ceramic. This trend was also observed for all of the disclosedstarting glass compositions when cerammed using Schedule 1 and was thebasis for selecting the Ta_(2-x)Al_(x)O_(5-x) glass-ceramics as thepreferred disclosed glass-ceramics. For all examples for which E, H, andnD data are listed in Table 1 or 2, the value of each of E, H, and nD isalways the greatest for the sample cerammed according to Schedule 1,i.e., the Ta_(2-x)Al_(x)O_(5-x) glass-ceramic.

Table 1 contains the undoped (i.e., without the transition metal oxidedopants or rare earth oxide dopants) Examples 1 to 21. Table 1 includes:compositional data in both mol and wt %; property data on the annealedglasses; property data on the Ta_(2-x)Al_(x)O_(5-x) glass-ceramicscerammed at 925° C. for 2 hrs; the crystal phase for each ofglass-ceramic as observed by XRD; the appearance description; andproperty data for the AlTaO₄ and AlPO₄ glass-ceramics cerammed at 875°C. for 2 hrs followed by 1075° C. for 2 hrs. The samples of thetransparent glass-ceramic compositions listed in Table 1 typically had aslight yellow or pale amber color, which may alternatively be indicativeof minor iron contamination during work up.

FIGS. 1 to 2 and FIGS. 4 to 6 are related to composition Example 4 inTable 1, while the photomicrograph images in FIG. 3A (lower temperatureceramming) and FIG. 3B (higher temperature ceramming) are also forcomposition Example 4 in Table 1.

Table 2 contains the doped (i.e., with a transition metal oxide dopantor rare earth oxide dopant) Examples 22 to 26.

Regarding dopants, in antiquity erbia oxide (Er₂O₃, i.e., a Ersesquioxide) was used as a pink coloring agent in glazes and glasses.Modernly, erbia has been used as a luminescent dopant to providefluorescence at 1.55 microns and is useful, for example, in opticalamplifiers for telecommunications. The 1.55 microns wavelength isespecially important for optical communications since standard singlemode optical fibers have minimal loss at this particular wavelength.

In embodiments, the disclosure provides an optical article, such as alens, a fiber, an amplifier component, and like articles, comprising: atransparent glass-ceramic composition including, for example, 65 to 75%SiO₂; 10 to 25% Al₂O₃; 5 to 15% Ta₂O₅; and 3 to 10% P₂O₅, based on 100mol % total.

In embodiments, the optical article can further comprise, for example, adopant comprising an oxide selected from Cr, Ni, Co, V, Mn, Cu, Er, or amixture thereof.

In embodiments, the optical article can further comprise, for example, asupplement selected from the formulas M_(x)O_(y) or M_(x)M′_(x′)O_(y),where M or M′ is selected from the group of a source of Nb, Ti, W, Al,or a mixture thereof, x and x′ are independently an integer from 1 to 2,and y is an integer from 1 to 5.

In embodiments, the disclosure provides an optical apparatus includingthe abovementioned optical article. In embodiments, the opticalapparatus can be, for example, an optical fiber, such as a single modefiber or a multimode fiber, a component of an optical amplifier for usein telecommunications, and like optical apparatus.

Tabulated Results

Exemplary examples of the disclosed transparent glass-ceramics arelisted in Table 1 (i.e., Si—Al—Ta—P transparent glass-ceramiccompositions and free of a dopant) and Table 2 (i.e., Si—Al—Ta—Ptransparent glass-ceramic compositions and containing a dopant). Thedisclosed sample compositions were characterized and their propertiesare also listed in Tables 1 and 2. Selected samples listed in Table 1,i.e., tabulated examples 1, 4, 6, 7, 8, 10, and 11, were cerammedaccording to Schedule 2 (i.e., 875/2, and then 1100/2) and they were allunexpectedly transparent after cooling to ambient temperature.Similarly, selected samples listed in Table 2, i.e., tabulated examples25 and 26 were cerammed according to Schedule 2 (i.e., 875/2, and then1100/2) and they were also unexpectedly transparent after cooling toambient temperature.

Table 3 lists examples of the aforementioned Si—Al—Ta—P transparentglass-ceramic compositions free of dopant that have at least onesupplemental metal, i.e., a portion (e.g., 0.1 to 50 mol %) of the Tacontent is substituted or replaced with, for example, Nb, Ti, or W, toproduce a Si—Al—Ta—P—Nb, a Si—Al—Ta—P—Ti, or a Si—Al—Ta—P—W transparentglass-ceramic composition.

Table 3 lists four compositions that demonstrate replacement of aportion of the Ta with, for example, Nb, Ti, or W, using, for example, asuitable source or oxide such as Nb₂O₅, TiO₂, or WO₂. The replacement orsupplemental metal compositions results in compositions havingtransparent glass-ceramic properties and having the same phaseassemblages, i.e., Ta₂O₅ (Ta_(2-x)Al_(x)O_(5-x)) at low ceramtemperature (e.g., 925/2 schedule 1), and AlTaO₄ and AlPO₄ at high ceramtemperature (e.g., 875/2, 1075/2 schedule 2). Unexpectedly, thereplacement or supplemental metal compositions example compositions A,B, and C, retain transparency up to a temperature of as high as 1100° C.Although not limited by theory, the presently disclosed transparentglass-ceramics are the only glass-ceramics that are transparent whenheated above 1000° C. (1832° F.), i.e., the transparency of thecomposition remains at of from 1,000 to 1,100° C. Although not limitedby theory, the Ta content in the disclosed compositions when combinedwith selected ceramming conditions appears to provide or insuresglass-ceramic transparency by, for example, limiting the size of thecrystallites or microcrystals. The Ta content in the compositions ofabout 5 mol % or more appears to assure glass-ceramic transparency,i.e., a glass-ceramic transparency agent.

The tabulated properties of the disclosed transparent glass-ceramicshave abbreviated labels:

-   -   T_(str) is the strain point;    -   T_(ann) is the anneal point;    -   T_(s) is the softening point;    -   a300 (i.e., alpha three hundred) is the average thermal        expansion coefficient (also known as linear coefficient of        thermal expansion or CTE) from ambient such as room temperature        25° C. to 300° C. in 10⁻⁷/° C.;    -   T_(g) is the glass transition temperature;    -   T_(x) is the onset of crystallization temperature;    -   r is the density in g/cc;    -   n is the Poisson's ratio;    -   nD or nD is the refractive index at the Na D line;    -   E is the Young's elastic modulus in GPa;    -   G is the shear modulus in GPa; and    -   H is the hardness in GPa.

The tabulated compositions also have abbreviated labels where:

-   -   “Ta₂O₅” is an abbreviation for the formula Ta_(2-x)Al_(x)O_(5-x)        crystal phase identified by x-ray diffraction, where x in this        formula is less than 1 such as 0.5, 0.4, 0.3, 0.2, 0.1, 0.005,        0.001, and like values, including intermediate values and        ranges.

“AP” is an abbreviation for the AlPO₄ crystal phase identified by x-raydiffraction.

-   -   “AT” is an abbreviation for the AlTaO₄ crystal phase identified        by x-ray diffraction.    -   “AT+AP” is an abbreviation for a mixture of AlTaO₄ and AlPO₄        crystal phases.

TABLE 1 Transparent glass-ceramic compositions free of dopant.Composition Example 1 2 3 4 5 6 7 8 9 10 mol % Ta₂O₅ 8 7 8 9 8 7 10 10 89 Al₂O₃ 14.5 14.5 17.5 15 16 15.5 15.5 14 13 15 P₂O₅ 7.5 7.5 4.5 6 6 7.54.5 6 9 8 SiO₂ 70 70 70 70 70 70 70 70 70 68 SnO₂ — 1 — — — — — — — — wt% Ta₂O₅ 34.4 30.9 34.8 37.6 34.6 31.1 40.7 40.5 34.2 37.1 Al₂O₃ 14.414.8 17.5 14.5 16 15.9 14.6 13.1 12.8 14.3 P₂O₅ 10.4 10.7 6.28 8.06 8.3310.7 5.89 7.81 12.3 10.6 SiO₂ 40.9 42.1 41.4 39.8 41.1 42.3 38.8 38.640.6 38.1 SnO₂ — 1.51 — — — — — — — — nD — — — 1.569 — — — — — — Tstr (°C.) 823 817 — — — — — — — — Tann (° C.) 871 869 — — — — — — — — a30012.4 12.5 — — — — — — — — Tg (° C.) 836 — 836 823 829 838 819 818 840835 Tx (° C.) 959 — 1057 958 987 1036 947 917 — — r (gm/cc) — — — 3.117— — — — — — E (GPa) 79.4 — — 82.9 83.4 79.4 89.3 84.3 76.5 79.7 G (GPa)32.8 — — 34.4 34.3 33 36.6 35 31.9 33.1 n 0.208 — — 0.205 0.213 0.2030.219 0.206 0.198 0.204 H (GPa) — — — 7.23 — — — — — — Schedule 1 Ta₂O₅Ta₂O₅ Ta₂O₅ Ta₂O₅ Ta₂O₅ 925/2 ceram appearance transp. — — transp. — — —transp. transp. transp. nD 1.558 — — 1.581 — — — 1.589 — 1.572 a300 — —— — — — 22.0 17.6 — 15.1 r (gm/cc) — — — 3.153 — — — — — — E (GPa) 82.2— — 87.1 — — — 87.6 77.6 82.8 G (GPa) 34.1 — — 36.3 — — — 36.6 32.7 34.5n 0.204 — — 0.201 — — — 0.204 0.187 0.198 H (GPa) — — — 7.89 — — — — — —Schedule 2 AT + AT + AT + AT + AT + AT + AT + AT + AT + AT + 875/2, thenAP AP AP AP AP AP AP AP AP AP 1075/2 ceram appearance transp. hazy —transp. transp. transp. transp. transp. transp. transp. nD 1.548 — —1.565 — — — 1.572 — 1.558 r (gm/cc) — — — 3.157 — — — — — — E (GPa) 70.4— — 79.1 61.4 58.3 77.2 71.4 53.6 59.6 G (GPa) 30.6 — — 33.8 27.1 25.733.6 30.7 24.5 26.3 n 0.149 — — 0.17 0.134 0.134 0.149 0.164 0.097 0.132H (GPa) — — — 7.67 — — — — — — Example 11 12 13 14 15 16 17 18 19 20 21mol % Ta₂O₅ 9.5 8 11 9.5 11 8 9.5 11 12.5 9.5 8 Al₂O₃ 16 13 18.5 18.5 1718.5 17 15.5 17 15.5 17 P₂O₅ 8.5 7 5.5 7 7 8.5 8.5 8.5 5.5 10 10 SiO₂ 6672 65 65 65 65 65 65 65 65 65 wt % Ta₂O₅ 38.1 34.7 42.5 38.2 42.3 33.538 42.1 46.2 38 33.4 Al₂O₃ 14.8 13 16.5 17.2 15.1 17.9 15.7 13.7 14.514.2 16.4 P₂O₅ 11 9.76 6.83 9.04 8.64 11.5 10.9 10.4 6.53 12.8 13.4 SiO₂36 42.5 34.1 35.5 34 37.1 35.4 33.8 32.7 35.2 36.9 Tg (° C.) 829 832 822830 825 835 834 821 831 851 849 Tx (° C.) — — 967 997 933 961 933 9161017 r (gm/cc) 3.11 — 3.388 — — — — 3.234 — — — E (GPa) 81.4 77.2 90.585.7 86.8 81.5 82.1 81.8 — — — G (GPa) 33.6 32.9 37.1 35.2 35.6 33.633.9 33.9 — — — n 0.212 0.174 0.22 0.217 0.218 0.211 0.213 0.205 — — — H(GPa) 6.44 — 7.5 — — — — 6.98 — — — — — — Schedule 1 Ta₂O₅ — — — Ta₂O₅ —— — — — — 925/2 ceram appearance transp. — — — transp. — — — — — — nD1.577 — — — 1.604 — — — — — — r (gm/cc) 3.137 — — — — — — 3.258 — — — E(GPa) 83.7 81.7 — — 90.5 — 85.4 85.5 — — — G (GPa) 34.8 34.1 — — 37.3 —35.3 35.4 — — — n 0.198 0.197 — — 0.213 — 0.21 0.207 — — — H (GPa) 7.45— — — — — — 7.41 — — — Schedule 2 AT + AP — AT + AP AT + AP AT + AP — —— — — — 875/2, then 1075/2 ceram appearance transp. — transp. transp.transp. — — — — — — nD 1.565 — 1.596 — 1.588 — — — — — — r (gm/cc) 3.16— 3.478 — — — — 3.288 — — — E (GPa) 61.6 66.2 77.7 66.7 66.3 60.9 67.265.6 — — — G (GPa) 27.2 28.9 33.4 29.1 29 26.8 29.4 28.7 — — — n 0.1350.145 0.165 0.147 0.146 0.139 0.144 0.144 — — — H (GPa) 6 — 8.43 — — — —7.56 — — —

TABLE 2 Transparent glass-ceramic compositions including a dopant.Example 22 23 24 25 26 mol % Ta₂O₅ 9 9 9 9 9 Al₂O₃ 15 15 15 15 15 P₂O₅ 66 6 6 6 SiO₂ 70 70 70 70 70 Cr₂O₃ 0.017 — — — — NiO — 0.035 — — — CoO —— 0.033 — — Er₂O₃ — — — 0.015 0.075 wt % Ta₂O₅ 37.6 37.6 37.6 37.6 37.5Al₂O₃ 14.5 14.5 14.5 14.5 14.4 P₂O₅ 8.06 8.06 8.06 8.05 8.04 SiO₂ 39.839.8 39.8 39.8 39.7 Cr₂O₃ 0.024 — — — — NiO — 0.025 — — — CoO — — 0.023— — Er₂O₃ — — — 0.05 0.27 Schedule 1 Ta₂O₅ Ta₂O₅ Ta₂O₅ Ta₂O₅ Ta₂O₅ 925/2ceram Appearance, trans- transp., transp., transp., transp., colorparent, amber blue amber amber green Schedule 2 AT + AP AT + AP AT + APAT + AP AT + AP 875/2, then 1075/2 Appearance, trans- transp., transp.,transp., transp., color parent, amber blue amber amber green

TABLE 3 Metal supplemented transparent Ta containing glass-ceramiccompositions. Example A B C D mol % Ta₂O₅ 6.75 4.5 6.75 6.75 Nb₂O₅ 2.254.5 — — TiO₂ — — 2.25 — WO₃ — — — 2.25 Al₂O₃ 15 15 15 15 P₂O₅ 6 6 6 6SiO₂ 70 70 70 70 wt % Ta₂O₅ 29.3 20.3 30.6 29.5 Nb₂O₅ 5.88 12.2 — — TiO₂— — 1.84 — WO₃ — — — 5.17 Al₂O₃ 15.0 15.6 15.7 15.2 P₂O₅ 8.37 8.71 8.738.44 SiO₂ 41.4 43 43.1 41.7 Tg (° C.) 800 773 816 813 Tx (° C.) 927 927927 927 Schedule 1 Ta₂O₅ Ta₂O₅ + Ta₂O₅ + Ta₂O₅ 925/2 ceram AT APAppearance transp. transp. translucent transp. Schedule 2 AT + AP AT +AP AT + AP AT + AP 875/2 and 1075/2 ceram Appearance transp. transp.transp. transp.

TABLE 4 Crystalline assemblage(s) at selected ceram temperatures.Temperature (° C.) Crystalline Assemblage(s) Present 900 Ta₂O₅ 925 Ta₂O₅950 Ta₂O₅ 975 Ta₂O₅ + AlTaO₄ 1000 Ta₂O₅ + AlTaO₄ 1025 AlTaO₄ + Ta₂O₅ +AlPO₄ 1050 AlTaO₄ + AlPO₄ 1075 AlTaO₄ + AlPO₄ 1100 AlTaO₄ + AlPO₄

TABLE 5 Boron-containing Ta₂O₅ or AlTaO₄ transparent glass-ceramics; andGa-containing Ta₂O₅ or AlTaO₄ transparent glass-ceramics. Example I IIIII IV V mol % Ta₂O₅ 9 9 9 9 11 Al₂O₃ 15 15 11.25 7.5 12.75 Ga₂O₃ — —3.75 7.5 4.25 P₂O₅ 6 6 6 6 7 SiO₂ 68 66 70 70 65 B₂O₃ 2 4 — — — wt %Ta₂O₅ 37.6 37.5 36.4 35.4 40.9 Al₂O₃ 14.4 14.4 10.5 6.81 10.9 Ga₂O₃ — —6.44 12.5 6.7 P₂O₅ 8.04 8.03 7.8 7.58 8.36 SiO₂ 38.6 37.4 38.5 37.4 32.9B₂O₃ 1.32 2.63 — — — Tg (° C.) 800 780 796 774 798 Tx (° C.) 929 911 899867 883 Schedule 1 Ta₂O₅ Ta₂O₅ + Ta₂O₅ + Ta₂O₅ + Ta₂O₅ + 925/2 AT AT ATAT Appearance slight haze slight haze slight haze slight haze slighthaze Schedule 2 AT + AP AT + AP AT + AP AT + AP AT + AP 875/2, then1075/2 Appearance transp. transp. transp. transp. transp.

The disclosure has been described with reference to various specificembodiments and techniques. However, many variations and modificationsare possible while remaining within the scope of the disclosure.

What is claimed is:
 1. A transparent glass-ceramic composition,comprising: 65 to 75% SiO₂; 10 to 25% Al₂O₃; 5 to 15% Ta₂O₅; and 3 to10% P₂O₅, based on 100 mol % total.
 2. The transparent glass-ceramiccomposition of claim 1, further comprising: SnO₂ in from 0.01 to 2 mol%.
 3. The transparent glass-ceramic composition of claim 1, wherein theTa₂O₅ content is of from 5 to 14 mol %.
 4. The transparent glass-ceramiccomposition of claim 1, wherein the Ta₂O₅ is of from 8 to 12 mol %. 5.The transparent glass-ceramic composition of claim 1, wherein thetransparency of the composition is retained at of from 1,000 to 1,100°C.
 6. The transparent glass-ceramic composition of claim 1, wherein thecomposition has a refractive index is from 1.55 to 1.61; the elasticmodulus is from 50 to 95 GPa; and the hardness is from 6 to 9 GPa. 7.The transparent glass-ceramic composition of claim 1, wherein thecomposition has a crystallite size of from 5 to 25 nm.
 8. Thetransparent glass-ceramic composition of claim 1, further comprising: adopant selected from a transition metal oxide or a rare earth oxide, inan amount of from 0.01 to 1 mol % based on the 100 mol %.
 9. Thetransparent glass-ceramic composition of claim 8 wherein the dopant isselected from Cr₂O₃, NiO, CoO, Er₂O₃, or a mixture thereof.
 10. Atransparent glass-ceramic composition, comprising: 65 to 72% SiO₂; 10 to20% Al₂O₃; 8 to 13% Ta₂O₅; and 4 to 9% P₂O₅, based on 100 mol %.
 11. Thetransparent glass-ceramic composition of claim 10, wherein thecomposition has a main crystalline phase of the formula Ta_(2-x),Al_(x)O_(5-x) where x is less than 1 and greater than 0.001.
 12. Thetransparent glass-ceramic composition of claim 10, wherein thecomposition has a refractive index is from 1.55 to 1.61; the elasticmodulus is from 50 to 95 GPa; and the hardness is from 6 to 9 GPa. 13.The transparent glass-ceramic composition of claim 10, wherein thecomposition has a crystallite size of from 5 to 25 nm.
 14. Thetransparent glass-ceramic composition of claim 10, further comprising: adopant selected from a transition metal oxide in an amount of 1 mol % orless based on the 100 mol %. 15-19. (canceled)
 20. A metal supplementedtransparent glass-ceramic composition, comprising: 65 to 75% SiO₂; 10 to25% Al₂O₃; 4 to 7.5% Ta₂O₅, 0.01 to 7.5% of M_(x)O_(y), M_(x)M′_(x′),O_(y), or a mixture thereof; and 3 to 10% P₂O₅, based on 100 mol %total, wherein in the formulas M_(x)O_(y) or M_(x)M′_(x′)O_(y), M or M′is selected from the group of a source of Nb, Ti, W, Al, or a mixturethereof, x and x′ are independently an integer from 1 to 2, and y is aninteger from 1 to
 5. 21. The transparent glass-ceramic composition ofclaim 20, wherein M is a Nb source in from 0.1 to 50 mol % of the Tacontent.
 22. The transparent glass-ceramic composition of claim 20,wherein M is a Ti source in from 0.1 to 25 mol % of the Ta content. 23.The transparent glass-ceramic composition of claim 20, wherein M is a Wsource in from 0.1 to 25 mol % of the Ta content. 24-29. (canceled)